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By G. T. Homce

Most electric motor predictive maintenance methods have drawbacks that limit their effectiveness in the mining environment. The U.S. Bureau of Mines is developing an alternative approach to detect winding insulation breakdown in advance of complete motor failure. In order to evaluate the analysis algorithms necessary for this approach, the USBM has designed and installed a system to monitor 120 electric motors in a coal preparation plant. The computer-based experimental system continuously gathers, stores, and analyzes electrical parameters for each motor. The results are then correlated to data from conventional motor-maintenance methods and in-service failures to determine if the analysis algorithms can detect signs of insulation deterioration and impending failure. This paper describes system design and implementation. At this writing, however, installation is still underway, and field data analysis results are not yet available.

Jan 1, 1994

By P. Songfack

In this work, the slurry flow in the ball mill is solved with Navier-Stokes' equations and the marker and cell technique (MAC), which tracks the fluid-free surface. Considering different planes in the radial and axial directions, this numerical approach leads to the direct calculation of the slurry velocity profile, mill holdup, and volumetric flow in the ball charge and pool. The MAC technique takes as input, the results of a direct three-dimensional simulation of the motion of grinding media, and in turn, provides a detailed knowledge of the hydrodynamics of slurry flow through the porous structure of ball load. This technique is a new approach to the mass transport problem that overcomes the limitations of indirect studies such as residence time analysis and holdup measurements.

Jan 1, 1994

By A. G. Kim

Increasing transportation costs, clean air regulations and the decreasing availability of landfill space are factors in the increased interest in the utilization of low cost disposal sites for coal combustion residues (CCR). Inactive surface and underground coal mines can satisfy the conditions for stable CCR disposal sites, and subsurface CCR injection can be beneficial in reducing the amount of acid mine drainage (AMD) often produced at such sites. The material is expected to add alkalinity to the subsurface environment and to decrease the permeability and porosity of the buried spoil. Both mechanisms can reduce the amount of acid normally generated at a mine site. The Bureau of Mines is cooperating with an independent coal company in a test of subsurface injection of a mixture of fly ash, from conventional power plants or from fluidized bed combustion (FBC) , with AMD sludge into a reclaimed surface mine. Changes in water quality parameters and the concentration of heavy metals in water samples from wells and seeps are being used to assess the effect of CCR injection. The preliminary results discussed here indicate that improvement in subsurface water quality was related to fly ash injection and that components of the fly ash were stable in the acid environment.

Jan 1, 1994

By Helmut Goehring

Surface mining has been used primarily where deposits of minerals were exposed or close to the surface. Surface mining can, therefore, be considered the oldest branch of mining. As the most accessible deposits became uneconomical because of the lack of suitable high capacity conveying systems, deep mining took its place. Only in the twentieth century was this trend reversed as high capacity production and conveying systems were developed. This rapid development was triggered by the steadily increasing demand for raw materials and fossil fuels, as well as by the ever increasing ratio between overburden and deposits.

Jan 1, 1982

By J. A. Baicker

A 2 1/2 inch diameter probe containing a high resolution gamma ray spectrometer was developed for downhole ore grade assays to depths of 6,000 feet. Tests have been conducted on the characteristics of this tool for in-situ determinations of uranium by means of natural gamma ray counting, and of copper, silver, gold, iron and coal quality by means of neutron-induced gamma rays. Application of the technique for improved carbon-oxygen logging in oil fields is promising. The probe contains a cryogenically cooled high purity germanium detector and a 4,000 channel spectrum analyzer. Gamma ray spectra are digitally transmitted up the cable to the truck-mounted data processing system. We found that uranium can be assayed directly in different types of formations independently of the degree of geochemical disequilibrium by counting the relatively weak 1.001 MeV gamma ray of protactinium-234m. Neutron activation work shows that in-situ determinations of copper, silver, iron and coal quality are technically feasible. In carbon-oxygen oil well logging the technique allows an accurate determination of carbon, oxygen, hydrogen, chlorine, silicon, calcium and iron, and shows promise of providing an improved oil/water differentiator.

Jan 1, 1982

By P. Diehl

The increasing public interest in a useful framework for an assessment and classification of mineral resources (1) is documented by the recently published international classification scheme of the United Nations (1979) and the revision of the classification system of USBM/USGS (2) (1980). Moreover, various classification systems are currently discussed by the mining industry. In spite of major improvements in respect of the concepts, definitions, and taxonomy of ore classification, it has been recognized that the recent practice to classify mineral resources does not create truly reproductible results, i.e. an assessment to the various categories which is free from personal bias or corporate interests. Following are geostatistical methods proposed for a standardization and quantification of various terms in ore classification. After critical review of present practices, we will establish a precise link between the classical terms such as "measured", "indicated", and "inferred" reserves and the geostatistical concept of estimation errors. Moreover, we will demonstrate, how the basic criteria of economic feasibility, geologic assurance and recovery can be taken into account by geostatistics. A specific algorithm will be proposed to block out and to classify reserves according to the degree of geologic assurance. . We will also show computerized methods which perform complete classification procedures, and will also exemplify them with typical case studies.

Jan 1, 1982

By Z. Yu

Dewatering of a -0.5 mm fine coal has been studied extensively. Deep cleaning requires however fine grinding, and dewatering of such ultrafine products presents a great challenge. Several coal samples finely ground and characterized by different wettabilities have b.een used in the filtration tests. Vacuum and press filters have been employed. In this paper only the results obtained with different flocculants (totally hydrophobic. semi-hydrophobic and hydrophilic polymers) are included. The results reveal the effect of coal surface properties and flocculant type on filtration of ultrafine coal.

Jan 1, 1994

By Gabino Preciado, Louis Sandbak

Corrosion has long been identified as a potential risk to the long-term ground support stability due to degradation of internal ground support elements such as rock bolts but also to surface support from mesh, straps, bolt plates, and ancillary support of utilities such as hangers. The emphasis is to understand the corrosion mechanisms on the primary ground support elements and any supplemental steel or arch sets. The water and chemical processes from oxidation(rust), stress corrosion cracking, and even the electrical charge created during these reactions contribute to the corrosion of the steel support elements. The main goals are to mitigate the effects of corrosion and to be able to predict those areas of high water or high sulphide for potential rehab maps. It is also essential to identify and classify the visible corrosion as part of damage mapping and provide bolt testing to those areas of suspected internal damage from corrosion. This is important to get an estimate of the support longevity or expected life before rehab to minimize the overall cost of the operation.

Feb 1, 2024

By G. L. Black

Choosing a mining method for an underground ore body is a complicated and often iterative process. Advances in technology give the design team an overwhelming array of possibilities for methods and equipment. Hecla's recent discovery of the deep Gold Hunter ore body has given the staff at the Lucky Friday Mine the exciting challenge of determining the optimum mining method. Taking an ore body from prospect to production requires traditional resource characterization, including drilling, delineating and modeling. Developing the mining plan is an evolving process, changing with each new piece of information as the project progresses through exploration and development.

Jan 1, 1998

By B. A. Ferguson, P. W. MacMillan

INTRODUCTION Jack Spalding in Deep Mining, Chapter 3, states: "In deep mining, to start stoping an orebody without a definite plan of operations covering the whole extraction from beginning to end is to invite serious trouble. Any stoping without plan is bound to leave, toward the end, a number of pillars, remnants, or promontories, which, as they are reduced in size, are liable to fail and cause a general collapse. The object of stope planning is so to mine an orebody that at no stage in the operation is a remnant left. Definition: `When a block of ore is stoped in such a way that eventually a small piece is left entirely surrounded by stoping, that piece is termed an island remnant.' The design of and adherence to a plan of stoping is of greater importance in preventing rock bursts than the type of ground control adopted." This, of course, is just an example of the old axiom that an ounce of prevention is worth a pound of cure. And in this context, mining does not have to be very deep before poor ground conditions, made worse by lack of good planning, force a mining company to resort to more expensive methods of ore recovery. At all times when rock pressures become excessive, stoping plans must be devised to avoid the creation of pillars or promontories. This is most readily recognized when mining deep narrow ore veins by open methods. It would be a little more general to say that stoping systems should seek to avoid or minimize localized concentrations of rock stress. Ore bodies, and particularly those at Falcon¬bridge, can reach large widths and leaving pillars for extraction at a later time cannot be avoided. However, good planning can reduce the effect of factors which create bad ground conditions. The necessary ingredients of planning are time and information: time to formulate and revise ideas; information, gained in exploration and early development, to provide the fullest knowledge of the ore body. In this way, plans become meaningful. It must always be kept in mind that the long-term results of good planning often require decisions not compatible with reaching earliest full production. PLANNING FOR DEEP MINING At Falconbridge Nickel Mines ore bodies presently being found and prepared for production lie at depths in excess of 610 m (2000 ft) below surface. Current un¬derground exploration is being directed towards favor¬able locations below 914.4 and 1219.2-m (3000 and 4000-ft) depths, at most mines. The Onaping Deep ore body has been traced to a depth of 1508.8 m (4950 ft) and at Falconbridge mine the ore body is under develop¬ment below the 5000 level. Planning for more efficient ground control has therefore become an important con¬sideration of future mining. HYDRAULIC BACK FILLING AND CUT-AND-FILL STOPING The advent of hydraulic back filling has led to the increasing use of flat-back cut-and-fill stoping methods during the last ten years, until it has probably become the commonest method of mining deep ore deposits in Canada. These methods account for almost all the pro¬duction from Falconbridge Mines at this time. The ad¬vantages claimed are: safety-a minimum of open ground; very little supplementary ground support (except rockbolted backs and walls); greater selectivity and flexibility in extraction (horizontal extension of the vein, high grade ore stringers going out into the walls); and high productivity and increased mechanization in larger ore widths. There is some difference of opinion as to whether hydraulic classified tailing back fill provides any great resistance to initial closure of the stope walls. The evi¬dence available suggests that it does not. Addition of portland cement to the back fill just prior to placement has produced a material having the properties of a weak concrete. It is confidently expected that this material will assist greatly in the efficient mining of pillars and generally in giving increased ground support to oppose closure. PRINCIPLES OF STOPE PLANNING BY LONGITUDINAL FLAT-BACK CUT-AND-FILL Again quoting from Spalding: "The practice of con¬trolling output by stopping and starting stopes is bad¬stopes once started should proceed without interruption, and control must therefore be obtained by altering the rate of stoping. It is therefore necessary that faces should normally advance at a medium rate which can be boosted, if required, to give temporarily a greater output. Modern high productivity stoping methods, however, generally aim to achieve and maintain the maximum output possible from a stope. Control of tonnage and grade, therefore, becomes a more complex problem requiring very careful scheduling and organiza¬tion. With the basic method of flat-back overhand stoping using hydraulic fill, it is not usually possible to mine in such a way as to avoid creating pillars." Consider an ore body as illustrated in Fig. 1. It is 274.3 m (900 ft) high by 228.6 m (750 ft) long on strike and averages 4.6 m (15 ft) in ore width. It rep¬resents approximately 907 000 t (1,000,000 st). The ore body could be mined by advancing one long single face through all the levels from bottom to top. A total face length of 228.6 m (750 ft) would accommo¬date five 45.7-m (150-ft) stopes. See Fig. la. Each of these stopes would produce approximately 1814 t/m (2000 stpm) and the ore body would require a period of ten years for complete extraction. A possible im¬provement to this scheme might be to stagger the indi¬vidual stope faces. See Fig. 1b. Problems of hanging wall failure can be reduced by this arrangement. From the point of view of reducing travelway maintenance, it is good practice to employ a stoping system of retreat. Stopes farthest from the shaft are mined first so that on completion, haulage drifts below can be aban

Jan 1, 1982

By Thomas P. Kwiatkowski, Len Cobb, Christopher D. Orlandi, Judith H. Jones

The Inland System supplies raw water to the industrial and domestic users in the City of Birmingham, Alabama. The Inland System, which is nearly 60 years old, consists of an approximately 57.9m (190 feet) high earthen dam across the Blackburn Fork of the Black Warrior River, a 39.6m (130 feet) high reinforced concrete intake structure, a 1524mm (60inch) diameter Dresser coupled steel transmission pipeline, and various distribution lines extending into Birmingham. The Inland System was owned, operated and maintained by the Industrial Water Board (IWB) of the City of Birmingham, an agency of the city government, from 1958 until 1994. In 1994, the City of Birmingham consolidated all water and distribution functions under the Birmingham Water Works Board (BWWB). In 1988, the IWB determined that the Inland System had reached a point where its reliability could not be assured without an in-depth evaluation and renovation. The IWB engaged Christy/Cobb, Inc. (CCI) of Birmingham as its consultant for the renovation work. CCI evaluated the Inland System and submitted a report to the IWB in April, 1992. The report contained several recommendations for capital improvements to the system including increasing the emergency spillway capacity, reconstructing the fuse plug, relocating public access to the lake away from the dam area, constructing a new intake structure, and constructing a tunnel through the dam abutment to deliver the water from the proposed intake structure to the existing 1524mm (60 inch) diameter supply line. The new intake structure and tunnel would provide for a future maximum demand flow rate as well as provide bypass and level control capabilities. CCI was authorized in 1992 to proceed with the engineering design for the renovation of the Inland System with emphasis on the spillway and intake structure. PROJECT DESCRIPTION The major component of the renovation of the Inland System was the new intake structure and tunnel through the dam abutment. CCI engaged Jenny Engineering Corporation (JEC) of Springfield, New Jersey as a consultant for the tunnel design. JEC was responsible for the design of the tunnel, the connecting shaft between the intake structure and tunnel, and the steel pipe final lining, while CCI was responsible for the intake structure and the connection to the existing supply pipeline as well as overall project management. CCI and JEC evaluated the project site in order to select the location for the new intake structure and set the alignment for the tunnel. A factor in the evaluation process was that the level of the lake could not be lowered to construct the new intake structure since the supply of water from the Inland System had to maintained. Therefore, a location was required which was

Jan 1, 1997

Lack of selectivity in mixed mineral flocculation can be attributed to one or more of the following factors: dissolved ion interference, heterocoagulation, mechanical entrapment in flocs and entrainment of fines between flocs. In a study of apatite- dolomite system, it was determined that dissolved ions do not have a significant effect on selectivity. Heterocoagulation was minimized by choosing proper process conditions and addition of a dispersant. Mechanical entrapment was proved to be insignificant and efforts were made to reduce entrainment by choosing an appropriate method of separation of flocs from fines. A new factor termed "polymer induced entrapment" which occurs due to limited affinity of the polymer to the mineral which is not flocculated is postulated to be the cause for the loss of selectivity.

Jan 1, 1986

By T. W. Lloyd

Accurately predicting coal seam discontinuities is an important part of modern underground coal mining. Conventional methods of coal exploration sometimes fail to identify rapid variations that may seriously impact mining and quality. Radio Imaging Method (RIM), a geophysical approach to mapping longwall panels, has been developed where electromagnetic signals are transmitted and received though the coal block. The amount of signal loss for a given distance, when compared to the coal seam characteristics, identifies anomalous areas. A comparison of RIM predictions with actual geologic conditions encountered during longwall mining demonstrates the accuracy and usefulness of the data.

Jan 1, 1986

By Y. Guan

The dissolution behavior of silver in ammoniacal solutions with cupric ammine as an oxidant has been investigated using a rotating disc electrode. The rates of dissolution of silver were determined by an electrochemical means as well as a direct measurement of silver ions reported in the bulk solution as a function of time. The variables investigated included stirring speed, temperature, concentration of lixiviants, and pH of the solutions. The rate of dissolution under the conditions studied' was found to be controlled by an electrochemical reaction at the liquid/ solid interface with an apparent activation energy of 48.07 kJ /mole. The rate was found to be a half order with respect to the, concentration of cupric tetra-ammine, Cu(NH3)l+.; The results were explained in terms of a mixed' potential theory.

Jan 1, 1994

By Y. S. Roditis

Traditionally, open pit optimization has been used to produce a single outline which can guide the pit design. This paper describes how a series of optimum nested pits are utilized to: a. produce different mining sequences and to help in mine planning and phase design; b. evaluate different metallurgical processes, production scenarios and equipment size; c. investigate the sensitivity of a project to prices, recoveries, production rates, costs, ultimate pit slopes etc.

Jan 1, 1993

By Robert L. Sundeen, Richard V. Wenberg

INTRODUCTION Shotcrete can be defined as spray-applied concrete with a maximum size aggregate in excess of 9.5 mm (0.375 in.). The concept evolved from guniting, which uses smaller aggregate and generally produces concrete with poorer physical properties. The larger aggregate used in shotcrete requires less water in the mix, while offering larger bonding surfaces, thus imparting greater tensile and compressive strengths. TYPES OF MACHINES Two basic designs of shotcrete machines in general use are the wet or prehydrated zero slump and low slump type, and the dry or nozzle hydrated machines. Fig. 1 shows a typical zero-slump machine in a con¬figuration commonly used for small-volume require¬ments. The prehydrated zero-slump machine mixes exactly proportioned batches in a sealed pressurized chamber. "Slugs" of hydrated shotcrete mix and com¬pressed air are sent through a distribution hose to the nozzle where the wet mix emerges as a spray. The spray is directed onto the rock surface by the nozzle operator. The low-slump machine is similar, except that a thick slurry mix of aggregate is delivered throughout the distribution hose to the nozzle. Fig. 2 shows a typical low-slump shotcrete machine used in moderate-volume applications. The nozzle-hydrated shotcrete machine accepts a premixed "dry" (4 to 6% moisture) batch of aggregate and cement. A constant feed of this mix is directed by compressed air through the distribution hose to the nozzle. At the nozzle, water for hydration is introduced into the emerging spray. The hydrated mixture is di¬rected onto the rock surface by the nozzle operator. Fig. 3 shows a typical dry-mix machine. The major difference between the two basic machine designs is the consistency of the shotcrete quality. Pre¬hydrated machines have high degrees of consistency and produce high-strength concrete, resulting from their ability to produce exact mixtures of zero or low-slump concrete within the machine. Nozzle-hydrated machines tend to produce poorer quality concrete because of the difficulty in controlling the water content at the nozzle. Water input essentially is an art. As such it is not precise, and the shotcrete produced is of variable quality. MATERIALS HANDLING Materials handling presents a problem to either type of shotcrete machine. At times considerable quantities

Jan 1, 1982

By D. K. Marjaniemi

The U.S. Bureau of Mines inventoried and characterized mineral sites and production plants within 200 km of the border in both the U.S. and Mexico. Sources of information included the USBM Minerals Availability System, the USBM Automated Mineral Information System, the USGS Mineral Resources Data System, the Mine Safety and Health Administration Address/Employment File, and the literature. Three hundred seventy-eight major construction material and industrial mineral properties were identified and characterized in the U.S. and Mexican parts of the Borderlands. Sixty-six major metallic mineral properties were identified and characterized in the Mexican part of the Borderlands.

Jan 1, 1996

By John W. Tieman

The increasing magnitude of our nation's pollution problems seems to stem from two main factors: urbanization and technical advance. In 1920, less than half the country's 106 million people lived in cities. Forty years later, the urban population accounted for 70 percent of the nation's 179 million. It is predicted that by the end of the century, 95 percent of the U. S. population, estimated at 280 million, will live in urban areas. As these people live increasingly in city concentrations, their residues also concentrate. With technological advances to support the increasing population, the variety and quantity of goods that we use also increases. New materials and processes result in increases in pollutants, some of them new. The harmfulness of these pollutants is sometimes known, but sometimes only suspected. One pollutant of concern at the present time is sulfur dioxide, the product of combustion of sulfur-containing fuels. Research on processes to remove sulfur oxides from flue gas has been in progress for many years. Pioneers in this field were the British who, in the early 1930's, installed a full-scale flue gas scrubbing unit on a 120 MW boiler using alkaline water from a Thames estuary plus chalk. Since that time, various methods have been studied by many investigators. Federal laws covering air pollution started with the 1955 Air Pollution Control Act. With the advent of the Air Quality Act of 1967, and subsequent publishing of criteria and available technology for control of sulfur oxides in January 1969, the clamor for information on commercially available control techniques to remove sulfur from fossil fuels has rapidly increased. Although many state-of-the-art papers have deluged the literature during the past several years, the research going on in the area of sulfur oxides control is of such importance that periodic reviews are justified. It is the purpose of this paper, therefore, to again review the state-of-the-art, but this time from the stand-point of what is immediately commercially available

Jan 1, 1972

By K. V. Raj, T. Bhowmick

"Computational fluid dynamics (CFD) modeling of an open-pit mine has several challenges. A good quality mesh of the model domain is a pre-requisite for convergence in solution. Good quality tetrahedral meshing and insertion of prism layers in faceted open-pit mine geometry is complicated due to presence of numerous vertices and ridges. Presence of vertices and ridges result in poor quality tetra elements and holes in prism layers, which cause instability in the model. Good quality pit bottom prism mesh elements significantly improve the formation of velocity boundary layer and thermal boundary layer at the pit bottom. This results in an expected temperature dependent micrometeorological buoyancy flow in the pit. Whereas, model geometry without a prism layer, results in abrupt temperature gradient near pit bottom. Buoyancy flow and recirculation have significant effect in lifting mechanism of fugitive dust particles generated near pit bottom. Representative initial and boundary conditions and selection of appropriate turbulence model have significant influences on the simulation results. In this paper, three-dimensional models of open-pit mines are developed using commercial CFD software (CRADLE-CFD). Important constraints and various consequences in modeling complex open-pit geometries are presented. INTRODUCTION Application of Computational fluid dynamics (CFD) to model an open-pit mine to predict fugitive dust and pollutant concentrations in and around a mine is relatively new. In former Soviet republic (USSR), Baklanov [1] and Belousov [2, 3] presented numerical models of pollutant transport in open-pit mines in Arctic regions. In recent years, advances in mathematical and computational fields have enabled better modeling of pollutant dispersion phenomenon around mines using computational fluid dynamics (CFD). Several CFD software packages have been used by various researchers to model the pollutant transport in open-pit mines. Works by Alvarez et al. [4]; Lowndes et al. [5]; Silvester et al. [6]; Torno et al. [7]; Choudhury and Bandopadhyay [8]; Collingwood et al. [9]; Raj et al. [10] and Flores et al. [11]; are examples of application of various commercial and open source CFD packages (COMSOL, ANSYS, OpenFOAM) to model pollutant transport in open-pit mines. These researches provided a strong background for additional research involving CFD modeling of open-pit mines. Due to the limitations of computational times and capacity, 3D modeling and various aspects of fugitive dust dispersion in open-pit mines remained unexplored."

Jan 1, 2015

By Surendra K. Mishra

With increasing regulatory pressure from the environmental authorities, waste management has become a focal point of industrial operation. To offset the waste management costs, industry has made conscious effort to recover usable resources from the waste streams. This paper reviews the technical developments and current practices in processing of waste materials. Methods for recovering metallic, non-metallic and organic species from solid wastes and effluents generated by operating plants are discussed.

Jan 1, 1997